1. Field of the Invention
The present invention relates to novel compounds, methods, and compositions capable of decreasing HIF hydroxylase enzyme activity, thereby increasing the stability and/or activity of hypoxia inducible factor (HIF).
2. State of the Art
Hypoxia inducible factor (HIF) is a basic helix-loop-helix (bHLH) PAS (Per/Arnt/Sim) transcriptional activator that mediates changes in gene expression in response to changes in cellular oxygen concentration. HIF is a heterodimer containing an oxygen-regulated α-subunit (HIFα), and a constitutively expressed β-subunit (HIFβ/ARNT). In oxygenated (normoxic) cells, HIFα subunits are rapidly degraded by a mechanism that involves ubiquitination by the von Hippel-Lindau tumor suppressor (pVHL) E3 ligase complex. Under hypoxic conditions, HIFα is not degraded, and an active HIFα/β complex accumulates in the nucleus, and activates the expression of several genes including glycolytic enzymes, glucose transporters, erythropoietin (EPO), and vascular endothelial growth factor (VEGF). (Jiang et al. (1996) J. Biol. Chem. 271:17771-17778; Iliopoulus et al. (1996) Proc. Natl. Acad. Sci. USA, 93:10595-10599; Maxwell et al. (1999) Nature 399:271-275; Sutter et al. (2000) Proc. Natl. Acad. Sci. USA 97:4748-4753; Cockman et al. (2000) J. Biol. Chem. 275:25733-25741; and Tanimoto et al. (2000) EMBO J. 19:4298-4309.)
Levels of HIFα are elevated in most cells in response to hypoxia, and HIFα is induced in vivo when animals are subjected to anemia or hypoxia. HIFα levels rise within a few hours after the onset of hypoxia, and induce numerous beneficial cellular processes including cytoprotective effects, enhanced erythropoiesis, and physiological adaptation to ischemic or hypoxic states. Induction of HIFα is potentially beneficial in conditions such as heart attack, stroke, peripheral vascular disease, chronic ischemia, inflammation, and anemia.
HIFα levels are also increased by a number of factors that mimic hypoxia, including iron chelators such as desferrioxamine (DFO), and divalent metal salts such as CoCl2. Additionally, several compounds originally identified as inhibitors of procollagen prolyl hydroxylase enzymes have been found to stabilize HIFα. Examples of such compounds can be found, e.g., in Majamaa et al. (1984) Eur. J. Biochem. 138:239-245; Majamaa et al. (1985) Biochem. J. 229:127-133; Kivirikko, and Myllyharju (1998) Matrix Biol. 16:357-368; Bickel et al. (1998) Hepatology 28:404-411; Friedman et al. (2000) Proc. Natl. Acad. Sci. USA 97:4736-4741; Franklin (1991) Biochem. Soc. Trans. 19):812-815; and Franklin et al. (2001) Biochem. J. 353:333-338. Additionally, compounds that stabilize HIFα have been described in, e.g., International Publication Nos. WO 03/049686, WO 02/074981, WO 03/080566, WO 2004/108681, WO 06/094292, WO 07/038,571, WO 07/090,068, and WO 07/103,905.
There remains a need for compounds that are effective in the treatment and prevention of conditions and disorders associated with HIF, including anemia and tissue damage caused by ischemia and/or hypoxia. Compounds are provided herein that modulate HIF and can thus be used to treat and prevent HIF-associated conditions and disorders including conditions involving anemia, ischemia, and hypoxia.